Primary phenomena associated with skin aging include a reduction in "moisture" and "elasticity", and the resulting wrinkles and "sagging". While the causes for this are not yet completely understood, it has been reported in J. Soc. Cosmet. Chem. Japan, 15, 77 (1981), Cell Structure and Function, 9, 357 (1984), Maria, et al., Carbohydrate Research, 159, 127-136 (1987) and elsewhere that one cause is believed to be an age-related decline in the production by skin cells of glycosaminoglycans such as hyaluronic acid, leading to a decrease in the moisture content of the skin which affects skin function. Based on this understanding, and in tandem with methods of forming an oily film on the skin surface for the purpose of passively preventing loss of moisture from the cuticle by perspiration, attention has been focused on the water retention properties of glycosaminoglycans, as a result of which hyaluronic acid derived from cockscombs and Streptococcus bacteria fermentation has been formulated into a variety of cosmetics for supplementation of a hydrophilic component, as a means of preventing wrinkles and "sagging"; however, since the hyaluronic acid in these cosmetics is simply applied onto the skin surface, the macromolecular hyaluronic acid is not absorbed into the skin and thus exhibits only a water-retention effect due to its hygroscopicity. The effect, then, is lost after washing, resulting in no substantial improvement in skin function. The only disclosed substance which activates skin cell function on the cellular level and enhances the production of glycosaminoglycans as water-retention components is egg enzymolysate, with its fractional components (Japanese Unexamined Patent Publication No. 5-271049).
Simple lysophospholipids, on the other hand, form extremely fine micelles in water due to their single-stranded structure, and thus yield fine emulsions in emulsified systems. They are characterized by having the effect of stabilizing emulsions and preventing starch aging (phenomenon of hardening and emergence due to recrystallization of starch molecules), and are thus used as emulsifiers and as modifiers for bread and the like. According to reports by Uchida, et al. (The Journal of Dermatology, 18, 523-527 (1991)), it has been demonstrated that lysophosphatidylcholine penetrates to the interior of the skin when applied to the skin surface of hairless rats without causing histological damage, and is thus highly safe as a cosmetic. This has led to the development of external skin preparations taking advantage of the safety, low irritancy and stable emulsifying effect of lysophospholipids (Japanese Unexamined Patent Publication No. 63-41411), but without dealing with their anti-aging effect on skin. Another example is Japanese Unexamined Patent Publication No. 3-161414 wherein lysophosphatidyl glycerol is formulated into a cosmetic for its water-retention effect; however, as in the case where hygroscopic hyaluronic acid is applied onto the skin surface, no effect can be expected once it is washed off.